We present an efficient algorithm for calculating the central path of a computer-generated colon model created from helical computed tomography image data. The central path is an essential aid for navigating through complex anatomy such as the colon. Our algorithm involves three steps. In the first step, we generate a 3D skeleton of the binary colon volume using a fast topological thinning algorithm. In the second step, we employ a graph search algorithm to remove extra loops and branches. These loops and branches are caused by holes in the object which are artifacts produced during image segmentation. In the final step, we compute a smooth representation of the central path by approximating the skeleton with cubic B-splines. This final step is necessary because the skeleton contains many abrupt changes in direction due to the discrete nature of image data. The user supplies two endpoints for the central path; otherwise, the algorithm is fully automated. Experimental results demonstrate that the algorithm is not only efficient but also robust. Use of this method in virtual endoscopy systems should have widespread clinical implications.